This invention relates to apparatus and a method for forming heated glass sheets while providing alignment between lower and upper molds used in the forming.
Glass sheets are conventionally formed by heating within a furnace and then forming within a heated chamber prior to delivery for cooling. Such cooling can be slow cooling to provide annealing or faster cooling that provides heat strengthening or tempering. In connection with heating of the glass sheets, see U.S. Pat. Nos. 3,806,312 McMaster et al.; 3,947,242 McMaster et al.; 3,994,711 McMaster; 4,404,011 McMaster; and 4,512,460 McMaster. In connection with glass sheet forming, see U.S. Pat. Nos. 4,282,026 McMaster et al.; 4,437,871 McMaster et al.; 4,575,390 McMaster; U.S. Pat. No. 4,661,141 Nitschke et al.; U.S. Pat. No. 5,004,491 McMaster et al.; and U.S. Pat. No. 5,472,470 Kormanyos et al. In connection with the cooling, see U.S. Pat. Nos. 3,936,291 McMaster; 4,470,838 McMaster et al.; 4,525,193 McMaster et al.; U.S. Pat. No. 4,946,491 Barr; and U.S. Pat. No. 5,385,786 Shetterly et al.
During the forming process, the heated glass sheets can be supported by a vacuum generated at a downwardly facing mold whose initial support of the glass sheet upon being received from a heating conveyor can be assisted by an upwardly directed heated gas flow that can be provided by gas jet pumps, such as disclosed by U.S. Pat. Nos. 4,204,854 McMaster et al. and 4,222,763 McMaster.
For effective high yield glass sheet forming, it is important for cooperable molds to be properly positioned upon mounting and aligned with each other during each cycle of operation therebetween, which is made more difficult due to the heated environment in which the glass sheet forming takes place. See, U.S. Pat. No. 4,781,745 Mumford; U.S. Pat. No. 5,158,592 Buckingham; U.S. Pat. No. 5,092,916 McMaster; and U.S. Pat. No. 5,230,728 McMaster. The heated environment also makes it more difficult to change molds between different production runs that cannot utilize the same molds. See U.S. Pat. No. 5,137,561 Schnabel, Jr. which discloses changing a cloth ring on a glass sheet heating furnace.
After forming, heat strengthening or tempering can be performed by rapid cooling at a quench section between lower and upper quench modules thereof and may have provision for transferring the glass sheet during such cooling by blowing a greater amount of gas upwardly so as to permit the associated quench ring that carries the glass sheet to move back to the heated forming station in preparation for the next cycle. See U.S. Pat. No. 4,361,432 McMaster et al.
All of the above cited patents are hereby incorporated by reference.
An object of the invention is to provide an improved method for forming a glass sheet.
In carrying out the above object, the method for forming a glass sheet is provided by heating the glass sheet during conveyance thereof on a horizontally extending conveyor. An upper mold is cyclically moved downwardly to receive the heated glass sheet from the conveyor and is then moved upwardly with the glass sheet supported thereby in preparation for the forming. A lower mold is then cyclically moved horizontally on a lower mold shuttle from an idle position horizontally spaced from the upper mold to a use position below the upper mold with the glass sheet supported thereby. The lower mold is then cyclically transferred in the use position from the lower mold shuttle to a lower mold support assembly, and thereafter the upper mold is cyclically moved downwardly toward the lower mold and the lower mold is moved horizontally on the lower mold support assembly as necessary into alignment with the upper mold whereupon the continued movement of the molds toward each other forms the glass sheet between the molds. Finally, the upper mold is cyclically moved upwardly and the lower mold is transferred from the lower mold support assembly back to the lower mold shuttle for horizontal movement thereon from below the upper mold back to the idle position to permit delivery of the formed glass sheet from the upper mold for cooling.
In the preferred practice of the method, the lower mold shuttle is supported by rollers during the horizontal movement on the lower mold between the idle and use positions, and the rollers are moved vertically to transfer the lower mold between the lower mold shuttle and the lower mold support assembly. The lower mold is locked on the lower mold shuttle to prevent movement with respect thereto along the direction of travel during the movement thereof between the idle and use positions.
In the preferred practice of the method, the formed glass sheet is deposited from the upper mold onto a quench ring for delivery to a quench station for quenching. The quench ring is moved on a quench shuttle and is locked with respect thereto during movement between the upper mold and the quench station but is unlocked at the upper mold to permit movement with respect to the quench shuttle into alignment with the upper mold.